Chewable tablet with herbal extracts and propolis arrests Wuhan and Omicron variants of SARS-CoV-2 virus

Abstract

Prevention of COVID-19 is of paramount importance for public health. Some natural extracts might have the potential to suppress COVID-19 infection. Therefore, this study aimed to design a standardised, efficient, and safe chewable tablet formulation (with propolis and three herbal extracts) for possible prevention against two variants (Wuhan B.1.36 and Omicron BA.1.1) of SARS-CoV-2 virus and other viral infections. Green tea, bilberry, dried pomegranate peel, and propolis extracts were selected for this purpose. Cytotoxicity and antiviral activity of each component, as well as the developed chewable tablet, were examined against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus using Vero E6 cells with the xCELLigence real-time cell analyser-multiple plates system. Anti-inflammatory and analgesic activities, as well as mutagenicity and anti-mutagenicity of the chewable tablet were also analysed. Compared to the control, it was observed that the chewable tablet at concentrations of 110 and 55 µg/mL had antiviral activity rates of 101% and 81%, respectively, for the Wuhan variant and 112% and 35%, respectively, for the Omicron variant. The combination of herbal extracts with propolis extract were synergically more effective (∼7-fold higher) than that of individual extract. The present work suggests that a combination of herbal extracts with propolis at suitable concentrations can effectively be used as a food supplement for the prevention of both variants of the SARS-CoV-2 virus in the oral cavity (the first entry point of the SARS-CoV-2 virus).

Keywords: Antiviral; COVID-19; Chewable tablet; Cytotoxicity; Extracts; Phenolics; Propolis.

Graphical abstract

Fig. 1

Cytotoxic effect of the chewable tablet on VERO E6 cell line.

Fig. 2

The antiviral activity of the chewable tablet against the Wuhan variant of the SARS-CoV-2 virus using the xCELLigence RTCA-MP system. Cell Index data were normalized and renamed NCI based on the time point at when the virus was added to the experiment. A) The xCELLigence system's cell index. Control Media: Vero E6 cells that were not infected with the virus (red line) and virus alone. Vero E6 cells that were infected with 3.5 × 10⁵ PFU/mL of the Wuhan variant of SARS-CoV-2 (B.1.36) (green line). B) The second graph depicts the same data but with the standard deviation included. C) The graph shows the antiviral activity rate of the chewable tablet sample.

Fig. 3

The antiviral activity of the chewable tablet against the Omicron variant of SARS-CoV-2 virus using the xCELLigence RTCA-MP system. Cell Index data were normalized and renamed NCI based on the time point at when the virus was added to the experiment. A) The xCELLigence system's cell index. Control Media: Vero E6 cells that were not infected with the virus (red line) and virus alone. Vero E6 cells that were infected with 1 × 10³ PFU/mL of Omicron variant of SARS-CoV-2 (BA.1.1) (green line). B) The second graph depicts the same data but with the standard deviation included. C) The graph shows the antiviral activity rate of the chewable table sample.

Fig. 4

Comparison of the effectiveness of the chewable table and its extracts against the Wuhan variant of SARS-CoV-2 virus using the xCELLigence RTCA-MP system.

Fig. 5

Effects of the chewable tablet on the viability of RAW264.7 macrophage cells. Abbreviation: IND, indomethacin.

Fig. 6

Effects of the chewable tablet on nitrite production in RAW 264.7 cells stimulated with 1 μg/mL of LPS. Statistical significant differences were indicated for each compound vs LPS (*p < 0.05). Abbreviations: LPS, lipopolysaccharides from E. coli; IND, indomethacin.

Fig. 7

Effects of the chewable tablet on PGE₂ production in RAW 264.7 cells stimulated with 1 μg/mL of LPS. Statistical significant differences were indicated for each compound vs LPS (*p < 0.05). Abbreviations: LPS, lipopolysaccharides from E. coli; IND, indomethacin.

Fig. 8

Anti-mutagenic activity (inhibition %) of the chewable tablet with and without metabolic activation (S9) in TA98 and TA100 strains. The anti-mutagenic activity was considered as follows: strong, the inhibitory effect was more than 40%; moderate, the inhibitory effect was between 25 and 40%; and weak, the inhibitory effect was < 25%, indicating no anti-mutagenic activity.